The long-term goal of our research is to define the details of the biochemistry of the replication of the DNA of selected small viruses. We examine the roles of host cell proteins in the catalysis and control of virus DNA replication. Virus DNA synthesis is being examined in mutant host cells defective in DNA synthesis genes. This allows us to define which host cell DNA synthesis proteins are necessary for virus DNA synthesis in cell free extracts of host cells. The emphasis in these in vitro studies is on the mechanisms by which host cell proteins initiate the synthesis of DNA chains on virus DNA templates.